This invention relates to an arrangement of a thread monitor at spinning stations of an open-end spinning machine containing a plurality of spinning stations, each of which spinning station is equipped with a thread monitor in each case, as seen in the take-off direction of a spun thread, after a thread take-off duct in the zone of take-off rolls.
It has been contemplated to locate a thread monitor, which interrupts the sliver feed in case of a thread breakage, directly at the exit of the thread take-off duct. This arrangement of the thread monitor causes difficulties if an automatic piecing operation is to be carried out after a thread has broken especially by means of a piecing device which can be moved along the open-end spinning machine. During this piecing operation, a thread end is returned via the thread take-off duct into the spinning rotor, attached to a fiber ring deposited at that point, and then taken off again. Care must be taken that, on the one hand, the thread monitor does not impede the return of the thread end, while, on the other hand, the return of the thread end must with certainty be effectd so that the thread, after being taken off again, lies on the correct side of the thread monitor.
In a conventional type of construction (German Pat. No. 2, 012, 108), a thread transfer gripper is designed in a special way for conducting the return of the thread end to the yarn take-off duct for a piecing operation. The thread transfer gripper is provided with an additional drive mechanism providing a relative movement with respect to the thread monitor and the thread take-off duct. Besides, an additional thread-guiding means is arranged at the transfer gripper, intended for a correct threading of the end of the yarn. These provisions considerably increase the structural expenditure for the piecing device. Furthermore, additional error sources are thereby created.
It has also been contemplated to dispose a thread monitor in the take-off direction of the spun thread directly in front of take-off rolls (DOS German Unexamined Laid-Open Application 2, 133, 135), so that thereby the region of the thread take-off duct can remain unimpeded. In this type of structure, no consideration is given to the fact that the spun thread should already change (reverse) in the zone of the take-off rolls, to prevent a premature wear and tear of the take-off rolls. However, such a changing step would mean that the spun thread would migrate by the same or a similar magnitude on the sensor of the thread monitor, so that the sensor of the thread monitor, customarily fashioned as a one-armed lever, is placed under differing loads. This would lead to differing response times in case of thread breaks, so that in certain cases different initial conditions prevail for a subsequent piecing operation, which can render the piecing step substantially more difficult.
The present invention contemplates arranging a thread monitor at a spinning station so that, on the one hand, the function of a piecing device is not impaired or made difficult while, on the other hand, the thread monitor is located in a zone having an exactly defined thread course.
In preferred embodiments of the invention, the thread monitors of the spinning stations are arranged on a traverse (reversing) rod which is located in front of the take-off rolls, as seen in the take-off direction of the spun thread. This arrangement has the result that the thread monitor is disposed in a zone wherein it does not impede the piecing operation, on the one hand, and executes concomitantly the desired traversing (changing, reversing) motion, on the other hand, so that the thread will constantly contact the same point of the sensor of the thread monitor. Any inaccuracies in the functioning of the thread monitor are thereby thus avoided.
These and other objects, features and advantages of the present invention will become more apparent from the following description when taken in connection with the accompanying drawings, which show, for purposes of illustration only, a single embodiment in accordance with the present invention.